Advanced Materials

A simple and general fabrication method for magnetic helical micromachines with or without claw-like protrusions is reported by Li Zhang and co-workers on page 811. The dynamics of motion control reveal that corkscrew motion can always be generated when the input frequency of the rotating magnetic field is sufficiently high. The micromachines exhibit excellent swimming behavior, low cytotoxicity, and are capable of 3D cargo transport in fluid.

The energy-efficient dehumidification over hier-archically porous metal-organic frameworks (MOFs) with hydrothermal stability is reported on page 806 by Jong-San Chang and co-workers. Their promising water sorption properties lead to a new type of advanced water adsorbents for the effective utilization of low-grade thermal energy as well as solar energy. These MOFs would be potential alternatives to commercial water adsorbents, which are used for industrial or indoor desiccant applications such as desiccant dehumidifiers/humidifiers, gas dryers, adsorptive air-conditioning systems, fresh water production, and adsorption heat transformation.

Scanning Kelvin probe microscopy (SKPM) measurements reveal a higher positive surface potential at the grain boundaries (GBs) as compared to the grain while conductive atomic force microscopy (C-AFM) measurements show higher current flow in the vicinity of the GBs of Cu₂ZnSnS₄ (CZTS) and Cu₂ZnSn(S,Se)₄ (CZTSSe). These results demonstrate the enhanced minority carrier collection taking place at the GBs of CZTS and CZTSSe.

For the first time the observation of substantial visible light-, electrically and mechanically induced changes of the magnetization of an organic exciton multiferroic consisting of single crystal P3HT doped with C₆₀ is reported. The observations open new avenues for exciton based spintronic devices.

The use of an ITO-free MoO₃/Ag/MoO₃ anode to control the photon harvesting in PCDTBT:PC₇₀BM solar cells is proposed. At first sight, the fact that these anodes possess reduced far-field transmission compared to ITO may seem to be a disadvantage. But, despite this, we show that by carefully tuning the resonant optical cavity we can enhance the external quantum efficiency close to the band edge of PCDTBT, resulting in high photocurrent and power conversion efficiency on par with ITO.

Kinetically assembled nanoparticles are fabricated from an advanced class of bioactive macromolecules that have potential utility in counteracting atherosclerotic plaque development via receptor-level blockage of inflammatory cells. In contrast to micellar analogs that exhibit poor potency and structural integrity under physiologic conditions, these kinetic nanoparticle assemblies maintain structural stability and demonstrate superior bioactivity in mediating oxidized low-density lipoprotein (oxLDL) uptake in inflammatory cells.

Unusually large thermopower modulation is demonstrated using a field effect transistor structure on a thermoelectric material. An electric field application provides an extremely thin (∼2 nm) two-dimensional electron gas (2DEG), which exhibits unusually large thermopower, approximately five times larger than that of the bulk. The present electric field induced 2DEG approach may accelerate the development of nanostructures for high performance thermoelectric materials.

Novel double-shelled CoMn₂O₄ hollow microcubes with nanometer-sized building blocks have been prepared by a facile co-precipitation and annealing method. In virtue of the unique structural features, the resultant CoMn₂O₄ hollow structures exhibit high specific capacity (∼830 mA h g⁻¹ at 200 mA g⁻¹) and good cycling performance as an anode material for lithium-ion batteries.

The ability of nano-hydroxyapatite (nHA) particles developed in-house to act as non-viral delivery vectors is assessed. These nHA particles are combined with collagen to yield bioactive, biodegradable collagen nano-hydroxyapatite (coll-nHA) scaffolds. Their ability to act as gene-activated matrices for BMP2 delivery is demonstrated with successful transfection of mesenchymal stem cells (MSCs) resulting in high calcium production.

The drug-loaded, transferrin and poly(ethylene glycol) (PEG)-functionalized gold nanoshells on silica nanorattles (pGSNs-Doc-Tf) can combine the active targeting, passive targeting, remote-controlled photothermal therapy together with chemotherapy to completely kill tumor cells via a single irradiation with near-infrared laser light.

A comprehensive study on the analogy of memristive magnetic tunnel junctions and biological neural systems is performed. It is demonstrated that the continuous, bipolar resistance change due to resistive switching can be used to mimic the synaptic connection between neurons. Particularly, the timing-dependent plasticity is observed. Further, the magnetization switching driven by spin-transfer torque in combination with back-hopping is used to generate current spikes. These spikes show remarkable similarities with the signals generated by excited neurons.

Drops of a particle-stabilised oil-in-water emulsion are encapsulated in air by using hydrophobic silica particles. Such systems, termed oil-in-water-in-air powdered emulsions, show free-flowing behavior. Successful preparation of the material is achieved by preventing oil droplets from creaming and coalescing.

The elastic deformation of few layers (5 to 25) of thick, freely suspended MoS₂ nanosheets by means of a nanoscopic version of a bending test experiment, carried out with the tip of an atomic force microscope is reported. Young's modulus of these nanosheets is extremely high (E = 0.33 TPa), comparable to that of graphene oxide, and the deformations are reversible up to tens of nanometers.

Porosity generally embrittles ceramics. In contrast to such expectations, this report demonstrates that an effective fracture strain of nanoporous silica aerogels increases with increasing porosity. At ultralow relative densities of <0.5%, nanoporous monoliths start exhibiting super-compressible deformation with effective fracture strains of >50%. This is attributed to consequences of an increase in the aspect ratio of ligaments with decreasing density.

The phase diagram of the redox active ionic liquid 1-methyl-3-propylimidazolium iodide (PMII) is examined as a function of temperature and iodine concentration. Beyond a threshold concentration of 3.9 M, the formation of higher polyiodides gives rise to a viscoelastic phase upon cooling. Despite of the very high viscosity of such polyiodide-containing PMII melts a strikingly high conductivity is maintained through Grotthuss-type bond exchange and ionic conduction.

An inorganic enhancement agent (EA) for high-intensity focused ultrasound (HIFU) imaging based on mesoporous silica nanocapsules is presented. The pronounced coagulative necrosis effects demonstrate, both in vitro and in vivo, that the EA can be developed as a highly promising theranostic agent for effective HIFU imaging and therapy owing to its high stability, efficient perfluorohexane loading and release, enhanced tumor ablation capability, and easy uptake by target tissues.

A periodically aligned submicron ZnO hemispheres array was embedded into a TiO₂ nanoparticulate thin film (thickness; ca. 12 μm) as a photoanode for dye-sensitized solar cells (DSSCs). The ZnO hemisphere array provided light scattering centers that excited more dyes and direct electron pathways to the electrodes, which is beneficial for high efficiency DSSCs.

Dirk Guldi and co-workers demonstrate on page 800 the realization of high-quality graphene flakes by means of solution processing with tightly interacting constituents to which a porphyrin has been self-assembled. These were integrated into novel photo-electrodes by means of layer-by-layer deposition that give rise to appreciable photocurrents.

Exfoliation of graphite by a positively charged pyrene derivative was achieved in water and electronic communication by non-invasive electrostatic interaction with a negatively charged porphyrin was accomplished and proven photospectroscopically. The oppositely charged components were assembled through layer by layer deposition.

Hierarchically porous metal–organic frameworks with mesoporous cages are demonstrated to behave as promising water adsorbents in energy-efficient dehumidification. Their low temperature desorption properties for water with huge sorption uptakes are essential for various water sorption applications including desiccant dehumidification and fresh water production.

A simple and general fabrication method for helical swimming micromachines by direct laser writing and e-beam evaporation is demonstrated. The magnetic helical devices exhibit varying magnetic shape anisotropy, yet always generate corkscrew motion using a rotating magnetic field. They also exhibit good swimming performance and are capable of pick-and-place micromanipulation in 3D. Cytotoxicity of the devices was investigated using mouse myoblasts.

Aligned oblique nanowire arrays (AONWAs; top image) with controllable obliquity, NW diameter, length, and density are produced by a novel method. A mechanism of array formation is proposed and it is demonstrated that the surface structure of AONWAs can be utilized to transport objects ranging from a polystyrene microsphere to a macroscopic PET sheet (lower figures). Unidirectional wetting of the surface and the relation between the anisotropy of the wetting and the NWs' obliquity are described. Potential applications of the AONWAs include fluidic diodes, drug delivery systems, and self-cleaning without a liquid.

In a film stack of bathocuproine (BCP) (electron transport layer), fac -tris(2-phenylpyridyl)iridium(III) [Ir(ppy)₃] blended in 4,4′-bis(N -carbazolyl)biphenyl (CBP) (light-emitting layer), and 4,4′,4″-tris(N -carbazolyl)triphenylamine (TCTA) (hole transport layer), the BCP and Ir(ppy)₃:CBP layers rapidly interdiffuse by anomalous Fickian diffusion. Diffusion leads to a decrease of up to 33% in the solid-state emission but no change in color.

All-organic photopatterned 4×4 one-diode–one-resistor (1D–1R) cell arrays are presented by Tae-Wook Kim, Alex Jen, and co-workers on page 828. The all-organic type photopatterned 4×4 1D–1R cell array architecture not only improves reading accessibility, but also prevents cross-talk with neighboring cells. Each 1D–1R cell in the array architecture shows excellent switching performance, which suggests that such memory devices can be used for future advanced nonvolatile memory applications.

An all organic, photopatterned 4 × 4 one diode-one resistor (1D–1R) cell array consisting of a photopatterned organic schottky diode and organic memory were fabricated and tested. Our results show that the all-organic type photopatterned 4 × 4 1D–1R cell array architecture not only improves reading accessibility, but also prevents cross-talk with neighboring cells. Each 1D–1R cell in the array architecture showed excellent switching performance, which suggests that such memory devices can be used for future advanced nonvolatile memory applications.

Transfer characteristics of ZnO thin-film transistors (TFTs) based on ZnO doped with various alkali metals. A new doping method is demonstrated by employing alkali metals to achieve high-performance and solution-processed ZnO TFTs with a low processing temperature (∼300 °C), which is applicable to flexible plastic substrates.

Macroscopic P3HT spherulitic crystals are grown in 25-nm-thick films via precise control of solvent swelling during polymer crystallization, which allow placement of transistor channels within single oriented crystal domains.Charge-transport anisotropy in the b–c (π-stacking & main chain) plane and the role of order–disorder grain boundaries are reported.

Realization of highly responsivity UV detectors is a critical challenge for accelerating the application of UV detectors. Exploiting nanoplasmonic enhancement, Ag nanoparticles have been formed on the GaN surface and the responsivity of the GaN UV detector has been enhanced about 30 times compared with that without Ag nanoparticles.